Bug report

Bug description:

Some PyMem_Realloc() / PyMem_RawRealloc() calls overwrite the original pointer directly.

If realloc fails, the old pointer is still valid, but it can be lost and leaked. See the comming PR for detail.

This is found using Claude Code.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-149931: Fix memory leaks on failed realloc #149932
• [3.15] gh-149931: Fix memory leaks on failed realloc (GH-149932) #150439
• [3.14] gh-149931: Fix memory leaks on failed realloc (GH-149932) #150476